The present invention concerns a travelling scanning apparatus for successively scanning the working conditions at each spinning position of a ring spinning machine with respect to end breakages, as well as to lap-up formations on drafting arrangement rolls.
Generally speaking, the travelling scanning apparatus is of the type comprising a yarn feeler checking the presence of a yarn between the delivery rolls of the drafting arrangement and the spindle without contacting the yarn. There is provided a second feeler which, in the event a yarn breakage which is detected, checks the presence of a fibre stream between the delivery rolls of the drafting arrangement and a broken yarn suction nozzle arranged directly below the bottom delivery roll in its normal working position. In order to detect the fibre stream, the fibre stream is deflected by a fibre stream deflecting device. An activating device, in the event of absence of a fibre stream, serves to activate an interrupting device interrupting the roving supply and which is provided at each spinning position of the ring spinning machine.
A ring spinning machine for the final spinning of the yarn comprises a large number of spinning positions, more than 400 as a rule, each position of which comprises a drafting arrangement in which the supplied fibre arrangement (also called roving) is drafted to the desired fineness and subsequently is twisted and spun into a yarn and wound up using a ring and spindle arrangement.
Notwithstanding continued efforts, there cannot be avoided the occasional occurrence of a yarn breakage between the drafting arrangement and the spindle at a spinning position of the ring spinning machine. This relatively rare event is very annoying in a spinning mill operation, as it involves loss of production and additional work. Furthermore, a loss of material is caused, as the loose fibres still emerging from the pair of delivery rolls of the drafting arrangement, which continues to operate, are no longer spun-in but are transferred to a collector via a suction nozzle of a broken yarn suction device.
Time and again it happens that these fibres do not move into the suction nozzle but lap-up about one or both delivery rolls. Such fibre lap-up increases in size as long as the fibre supply is not interrupted or the yarn formation is not resumed again, until finally the drafting arrangement of the spinning position concerned is damaged. It thus is important in the spinning mill operation to have the working conditions of the ring spinning machine scanned by the operating personnel and to have the broken ends pieced up, in which process any fibre lap-ups built up on the rolls are to be first eliminated.
Devices have become known recently, the object of which is the replacement of the ring spinning operators by automatic devices, namely by operating devices or scanning devices performing the following tasks:
(a) Recoginizing the working conditions at the spinning position, i.e. for instance, detection of a yarn formation, the presence of a fibre lap-up on the rolls of the drafting arrangement or of a roving at the entrance of the drafting arrangement. PA1 (b) Performing an actual operation at the spinning position, such as e.g. piecing the broken yarn, or stopping the supply of fibre material to the drafting arrangement. PA1 (a) the presence of a fibre stream between the delivery rolls of the drafting arrangement and the broken yarn suction nozzle in case of yarn breakage is reliably detected; PA1 (b) the function of the apparatus is substantially independent of its positioning along the machine, in such manner that no excessive requirements are imposed as to the precision of the guide arrangement for the apparatus; PA1 (c) the apparatus does not interfere in any manner with the function of the correctly operating spindle and functions without application of air streams; and PA1 (d) the apparatus is simple and economically feasible and does not demand much operating and maintenance labor.
Such operations are effected in dependence upon the recognized working conditions at the spinning position.
The present invention concerns the recognition of certain working conditions at the spinning position and the performance of a certain operation, namely the interruption of the material supply, in the event the danger of lap-up formation on a delivery roll of the drafting arrangement is detected.
Various solutions for this task have become known already.
Thus, it is known from Swiss Patent No. 571,588 (or German Patent Publication No. 2,339,654) for automatically piecing yarns on ring-spinning machines, that by using a scanning device the absence of the yarn as well as a lap-up on the delivery rolls is simultaneously detected. In this arrangement a light source is directed at the path of the strand of fibres emerging from the delivery rolls but not spun into a yarn, which strand reflects the light beam onto a photocell. With this proposed equipment there is relied on the fact that the path of the strand of fibres subject to the spinning-in process does not coincide with the path of the strand of fibres which no longer is spun-in and is sucked off via the fixedly located suction nozzle, but differs by a distance of the order of a few millimeters.
Travelling scanning devices of this type present the disadvantage that the optical scanning of the strand of fibres not spun-in, which flows to the suction nozzle as a stream of fibres, when using a light beam proves unreliable, as the path of the fibre stream suitable for scanning is very short. The suction nozzle of the broken yarn suction device (for ensuring the efficiency of the broken yarn suction action) must be located in the immediate vicinity of the nip of the delivery rolls, such that the deviation of the path as such is already very small. Due to the short scanning path available the reliability of the photocell is also rendered problematic, since the light beam, even in the absence of the strand of fibres, and particularly if the fibres lap-up about one of the delivery rolls, can be reflected by unintended reflecting surfaces (such as e.g. the surface of a fibre lap-up, the surface of the bottom delivery roll or the suction nozzle). Reliable detection of the working conditions prevailing at the spinning position, thus is not ensured. Furthermore, the known travelling device is associated with the disadvantage that very precise guidance of the device along the ring spinning machine is required, as the distance between the two paths mentioned for the strand of fibres is very small. Such precise guide arrangements imply considerable mechanical efforts.
Furthermore, from Swiss Pat. No. 578,059 there is known to the art a travelling scanning device for an automatic yarn piecing device for ring spinning machines, which among other components also comprises a device for the detection of fibre lap-up on the delivery rolls of the drafting arrangement. It consists of two wheels provided with axial openings, these wheels being installed in close vicinity to the periphery of the delivery rolls. If a fibre lap-up builds up, the wheel contacting the lap-up is set into rotation, which phenomenon is scanned optically. Instead of optical scanning also a contacting tongue is proposed for the metallic bottom delivery roll.
Mechanical scanning of the delivery roll also presents the disadvantage that there is required a very precise and expensive guiding arrangement for guiding the scanning device along the machine; its design also is relatively complicated, which adversely influences its price and its reliability.
Furthermore, from a not pre-published Swiss Application Ser. No. 10164/72 there has become known a scanning device of the type initially mentioned, in which there is provided a fibre stream deflection device. The fibre stream deflection or deflecting device serves the purpose of taking-up, in the case of a yarn breakage and controlled by a yarn detector, the fibre stream emerging from the drafting arrangement and carried by the suction air stream, by sucking it off and guiding it to a fibre detector.
This known scanning device has the disadvantage that a travelling suction source is required, which renders the device complicated and expensive.